ARM: dts: dra72-evm: Provide explicit pinmux for TPS PMIC

Even thought sys_nirq1 is hardwired on the SoC for the pin, it is
better to configure the pin to the required mux configuration.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>